It’s not pointless to lock the barn door after the horse has gone—if, that is, you still happen to have some horses remaining in the barn.

The political party of Sumner, Lodge, and Dewey retains a minimal presence in the Northeast: three Republican members of the House from New York and three Republican senators from New England. One of those senators—Judd Gregg of New Hampshire—will retire in 2010, but Maine’s Olympia Snowe does not face re-election until 2012 and Susan Collins just won re-election in Maine in 2008.

These New England senators are not as conservative as the rest of the Republican caucus. (Snowe and Collins both voted for the stimulus package.) They are, however, much more conservative than most of the Democratic caucus. (Both have opposed pro-union card-check legislation.)

It ought to be obvious to any Republican why we need to make room for politicians like Snowe and Collins in our party. It’s not like we have so many votes that we can afford to throw them away. And yet, some Republicans responded to the defection this week of Sen. Arlen Specter by saying: “Good riddance—don’t let the door hit you on the way out.” Others say they would prefer a Republican caucus of 30 principled conservatives in the Senate to a less ideologically pure 40-vote, center-right coalition.

If we’re not careful, these voices could cost us the rest of our presence in the Northeast, either by pushing more moderate senators to defect or by positioning the national GOP in such a narrow way that retaining those moderate seats is rendered impossible.

So what to do? How do we Republicans reverse this downward spiral?

First, how about we stop eating our own?

Over the past few years, we have seen a series of primary challenges by conservative Republicans against moderate incumbents.

Here are just a few examples:

In 2008, a conservative state senator defeated incumbent Republican Congressman Wayne Gilchrist in the Republican primary in Maryland’s first district. In the previous cycle, 2006, Michigan Rep. Joe Schwarz was upended in a primary by Tim Walberg. Both of these victorious conservatives proceeded to lose in their general elections, delivering Republican seats to Democrats. It was another such intra-party challenge—this time by conservative Pat Toomey—that drove Arlen Specter out of the Republican caucus. Specter knew he could not prevail in a primary against Toomey within today’s shriveled GOP. (He barely survived a challenge by Toomey in 2004.) Specter also knew that he enjoyed a very good chance to win a general election. His decision was obvious.

Second, Republicans have to find some way to make internal peace on the abortion issue. The GOP is a majority pro-life party, and so naturally the head of the ticket will tend to be pro-life as well. But New England and the mid-Atlantic are regions in which Republican officeholders tend to be pro-choice. Think Rudy Giuliani, George Pataki, Tom Ridge, Susan Collins, Olympia Snowe, Christie Todd Whitman. If we restrict pro-choice candidates from ever being considered for the national ticket, in effect we are placing a ceiling on the careers of Northeastern Republicans.

This is not merely a theoretical problem. In the last election, John McCain’s campaign team decided that winning Pennsylvania was essential to their strategy. Yet the most popular Republican in Pennsylvania, pro-choice former Gov. Tom Ridge, was ruled out for the No. 2 spot because of abortion politics. When the McCain team next decided to search for a woman, they had to disregard both New England senators, again because of abortion politics—and this in a party that had a grand total of only five women senators and governors to choose from.

Politicians are creatures of ambition. If a national party bars politicians of a certain region from the highest offices, those politicians will gravitate to places—and parties—where their ambitions can be gratified. By penalizing pro-choice candidates, Republicans are not only making their party increasingly unelectable in the present, they are repelling the very people who might help restore electability in the future.

Third, politicians have to be allowed some leeway to vote the interests of their constituencies. Southern Republicans who vote against base closings should not be shocked when Northeastern Republicans vote for Amtrak. A Member of Congress from Connecticut may well care more about the Alternative Minimum Tax than about the death taxes that incense members from farming and ranching states. A candidate in coastal New Jersey may understandably vote differently on environmental issues than a candidate from Oklahoma.

I’ve never heard anyone derided as a “Republican in Name Only” for opposing the closing of redundant military bases, or for supporting Medicaid reimbursement formulas that favor the South and the West at the expense of the Northeast and California, or for favoring lavish FEMA reconstruction projects after hurricanes and tornadoes. Why not apply equal latitude to other regional concerns?

Yes, regional concerns can be avenues to waste. We need budget hawks from every region. But there has to be some play in the system, a little more flexibility in determining which issues entail fundamental principle and which are open to normal politics.

That’s how we build national coalitions and national parties. Right now, I fear, the Republican mood is not conducive to party building. It’s a mandate for party shrinkage. Our current demand, to paraphrase P.G. Wodehouse, is for “fewer and better Republicans.” Better is always nice. But in democratic politics, quality is no substitute for quantity.